Operating characteristics of high continuous power (50 W)two-dimensional surface-emitting lase array

Monolithic two-dimensional surface-emitting laser (SEL) arrays suitable for both optoelectronic and high power applications were fabricated utilizing a 4-μm×450-μm InGaAs single mode real refractive index guided gain cavity with 90° and 45° ion milled facets. A total CW output power exceeding 50 W was achieved at λ≈944 nm from a monolithic 16×94 2-D SEL array. The 50-W CW output power level is approximately ten times greater than previously demonstrated from a 2-D monolithic SEL array. Greater than 150 h of continuous operation of a 2-D SEL array at 25 W CW was demonstrated     

GaInNAs-GaAs long-wavelength vertical-cavity surface-emitting laserdiodes

Vertical-cavity surface-emitting laser diodes with GaInNAs-GaAs quantum-well (QW) active layers are demonstrated for the first time. GaInNAs permits the realization of a long-wavelength vertical-cavity laser grown directly on a GaAs substrate. Room-temperature (RT) pulsed operation is achieved, with an active wavelength near 1.18 μm, threshold current density of 3.1 kA/cm², slope efficiency of ~0.04 W/A, and output power above 5 mW for 45-μm-diameter devices. Laser oscillation is observed for temperatures at high as 95°C     

Ho:YAG laser pumped by 1.9-μm diode lasers

A 21-μm Ho:YAG laser end pumped by 1.9-μm diode lasers has generated nearly 0.7-W CW output power. Laser operation was maintained even with Ho:YAG heat sink temperatures in excess of 60°C     

Low-threshold, high-power, 1.3-μm wavelength, InGaAsP-InPetched-facet folded-cavity surface-emitting lasers

A 1.3-μm wavelength, InGaAsP-InP folded-cavity, surface-emitting laser with CH₄-H₂ reactive ion-etched vertical and 45° angled facets was demonstrated for the first time. Continuous-wave threshold currents of 32 mA have been achieved, with >15 mW CW power for the surface-emitted light. These surface-emitting lasers with two dry-etched facets are suitable for wafer-level testing and for monolithic integration with other InP-based photonic devices     

High-temperature CW operation of InGaAsP-InP semi-insulating buriedheterostructure lasers using reactive ion-etching technique

We fabricated 1.5-μm semi-insulating buried heterostructure (SI-BH) lasers with InGaAsP-InP strained-layer multiple-quantum wells using a reactive ion etching (RIE) technique for mesa definition. A very high CW operating temperature of 150°C was obtained in a 300-μm-long laser whose rear facet was HR-coated     

Wavelength dependence of characteristics of 1.2-1.55 μmInGaAsP/InP p-substrate buried crescent laser diodes

Laser diodes with the p-substrate buried-crescent structure have been fabricated for the 1.2-1.55-μm wavelength region. The dependence of laser characteristics on wavelength has been measured. Up to 70°C, the increasing rates of the threshold current with temperature are similar, while, above 70°C, a shorter-wavelength laser shows a larger increasing rate. At the same full width at half maximum of the far-field pattern perpendicular to the junction plane, the external differential quantum efficiency of the 1.55-μm laser diode is only 10% smaller than that of the 1.3-μm laser. The absorption loss coefficients in the active layer of the 1.2-, 1.3-, and 1.55-μm laser are estimated to be 26, 34, and 73 cm^-1, respectively     

MOVPE growth of a monolithic VCSEL at 1.56 μm in theInGaAlAs-InAlAs system lattice matched to InP

The first demonstration of a one-step-growth vertical-cavity surface-emitting laser (VCSEL) at 1.56 μm by low-pressure metal-organic vapor phase epitaxy in the InGaAlAs (λ_gap=1.43 μm)-InAlAs system lattice matched to InP is presented. The VCSEL's threshold current density was 7.5 kA/cm² and pulsed lasing had been obtained up to +55°C for 45-μm diameter proton implanted devices. This material system represents a high potential for continuous-wave VCSELs at 1.55-μm wavelength using a simple approach for large-scale industrial production     

Method for setting the absolute frequency of a tunable, 1.5 μmtwo-section DBR laser

A technique for setting the absolute frequency of a 1.5-μm two-section distributed Bragg reflector (DBR) laser using an Er:YAG optical filter as a frequency discriminator is described. The absolute frequency of the laser was controlled with an accuracy better than 300 MHz over a tuning range of several hundred gigahertz. The frequency drift with laser temperature was -130 MHz/°C, and the tuning rate with current in the active region was 40 MHz/mA     

1.55-μm InGaAsP-InP spot-size-converted (SSC) laser with simpletechnological process

In this letter, we report the realization of a 1.55-μm spot-size-converted (SSC) laser using conventional SCH-MQW active layers and conventional photolithography. The laser consists of a 300-μm-long rectangular gain section, with compensated multiple-quantum-well (MQW) structure, and a 300-μm-long tapered passive waveguide, fabricated on lower SCH layer. The device exhibits a beam divergence of 13°×18° and 3.5-dB coupling loss with a cleaved single-mode fiber (SMF). The 1-dB alignment tolerance is ±2.3 μm in the vertical direction and ±1.9 μm in the lateral direction, respectively     

Ridge laser with spot-size converter in a single epitaxial step forhigh coupling efficiency to single-mode fibers

We report on a 1.55-μm InGaAsP MQW laser diode with an integrated spot-size converter fabricated in a single epitaxial step using conventional photolithography. The laser structure uses a conventional ridge guide for the active layers and a second larger ridge for the passive waveguide. Low-beam divergence of typically 9°×9° results in about 3-dB coupling losses, with a cleaved optical fiber     

Improving single-mode VCSEL performance by introducing a longmonolithic cavity

We report on the improvement of several selectively oxidized vertical-cavity surface emitting laser characteristics by introducing a long monolithic cavity. The samples compared are grown with various cavity lengths using solid-source MBE. The 980 nm-regime is chosen as emission wavelength to facilitate growth by using binary GaAs cavity spacers. A record high single-transverse mode output power of 5 mW at a series resistance of 98 Ω is obtained for a 7-μm aperture device with a 4-μm cavity spacer. Using an 8-μm cavity spacer, devices up to 16-μm aperture diameter emit 1.7 mW of single-mode power with a full-width at half-maximum far-field angle below 3.8°     

Low threshold room temperature pulsed and -57°C CW operationsof 1.3 μm GaInAsP/InP circular planar buried heterostructuresurface-emitting lasers

Room temperature pulsed lasing operation of a 1.3-μm GaInAsP/InP vertical-cavity surface-emitting laser has been achieved by using an effective carrier confinement of circular planar buried heterostructure (CPBH) and high reflectivity SiO₂/Si dielectric multilayer mirrors. The threshold current for a device having a nearly 12-μm-diameter active region was 34 mA at 24°C under pulsed operation. The optimized window cap structure reduces the series resistance to 6~15 Ω. Continuous wave lasing was also obtained up to -57°C, and the threshold below -61°C was still lower than 22 mA     

High output power and high temperature operation of 1.5 μmDFB-PPIBH laser diodes

Highly efficient 1.5-μm distributed-feedback (DFB) p-substrate partially-inverted buried heterostructure laser diodes with a thin active layer developed using a metal-organic chemical vapor deposition technique are discussed. An average slope efficiency of 0.26 mW/mA (quantum efficiency 33%) and maximum slope efficiency of 0.39 mW MW/mA (49%) were achieved. The full width at half maximum in the direction perpendicular to the junction plane of 25° was obtained. A high output power of 77 mW was obtained under CW conditions at room temperature. This laser diode lased up to 120°C, and more than 10 mW was obtained, even at 90°C     

Native-oxidized InAlAs blocking layer buried heterostructureInGaAsP-InP MQW laser for high-temperature operation

A novel idea of InAlAs native oxide utilized to replace the p-n-p-n thyristor blocking layer and improve the high-temperature performance of the buried heterostructure first proposed and demonstrated. A temperature (To) of 50 K is achieved from an InAlAs native oxide buried heterostructure (NOBH) InGaAsP-InP multiquantum-well laser with 1.5-μm-wide diode leakage passage path. The threshold current and slope efficiency of NOBH laser changes from 5.6 mA, 0.23 mW/mA to 28 mA, 0.11 mW/mA with the operating temperature changing from 20°C to 100°C. It is comparable to conventional p-n reverse biased junction BH laser with minimized diode leakage current, and is much better than the buried ridge strip with proton implanted laterally confinement laser     

Reflection loss of laser mode from tilted end mirror

The reflection of the lowest-order guided TE mode of a slab waveguide from a tilted end mirror is discussed. The problem is applicable to injection lasers if the slab is regarded as an effective refractive index approximation of the channel or ridge waveguide of the laser structure. For a mode width of 3 μm, 5° mirror tilt results in reflection losses in excess of 25 dB; for modes of 6-μm width, 5° mirror tilt causes reflection losses in excess of 45 dB. For small tilt angles the results of this calculation agree with those based on a Gaussian approximation of the guided mode. For larger angles, and hence higher reflection losses, the results depart significantly from the Gaussian approximation     

Wideband and high-power compressively strained GaInAsP/InPmultiple-quantum-well ridge waveguide lasers emitting at 1.3 μm

Compressively strained 1.3-μm GaInAsP/InP multiple-quantum-well (MQW) ridge waveguide lasers were fabricated. Through optimizing the total well thickness, large bandwidth over 11 GHz was achieved, together with high quantum efficiency of about 0.48 W/A and high power output of 60 mW before rollover. The laser also showed less temperature sensitivity up to an elevated temperature of 85°C     

Low-threshold tensile-strained InGaAs-InGaAsP quantum-well laserswith single-step separate-confinement heterostructures

The authors studied tensile-strained InGaAs-InGaAsP quantum-well lasers with single-step separate-confinement heterostructures (SCH). They obtained threshold currents below 2 mA at 20°C and below 10 mA at 100°C with indium mole fractions of 0.3 and 0.35 in the active layers. They found that the poorer carrier confinement of the longer wavelength SCH layer lowered the characteristic temperature at high temperatures. A laser with two In_0.35Ga_0.65As wells and a 1.1-μm composition InGaAsP SCH layer produced a 1.6-mA CW threshold current at 20°C and lasing at 120°C. Using this laser, very short lasing delays under zero-bias current over a wide temperature range and 2 Gb/s modulation under zero-bias current at 70°C were achieved     

A highly reliable GaInAs-GaInP 0.98-μm window laser

A novel window structure realized by selective N ion implantation and subsequent rapid thermal annealing has been applied to overcome the catastrophic optical damage (COD) of a GaInAs-GaInP laser emitting in the 0.98-μm wavelength region. A kink-free output power up to 220 mW at 25°C was obtained. Laser characteristics including the I-L, far-field pattern, and lasing spectrum were almost the same as those of a conventional nonwindow laser consisting of the same structure except for the window region. In a 50°C, APC-150 mW aging test, the window lasers have operated stably beyond 16 000 h, and no damage has been observed. Under this aging condition, a median lifetime of 280 000 h was obtained from log-normal plotting of aging characteristics. This marked improvement in reliability is due to a remarkable increase of damage tolerance realized by the window structure. In addition, there was minimal change in the characteristic of the window laser during the aging, indicating the absence of serious inner degradation. These results clearly show that our 0.98-μm window laser suppresses both COD failure and inner degradation satisfactorily and can be used in practical applications     

High temperature, high power InGaAs/GaAs quantum-well lasers withlattice-matched InGaP cladding layers

The authors report the high-temperature and high-power operation of strained-layer InGaAs/GaAs quantum well lasers with lattice-matched InGaP cladding layers grown by gas-source molecular beam epitaxy. Self-aligned ridge waveguide lasers of 3-μm width were fabricated. These lasers have low threshold currents (7 mA for 250-μm-long cavity and 12 mA for 500-μm-long cavity), high external quantum efficiencies (0.9 mW/mA), and high peak powers (160 mW for 3-μm-wide lasers and 285 mW for 5-μm-wide laser) at room temperature under continuous wave (CW) conditions. The CW operating temperature of 185°C is the highest ever reported for InGaAs/GaAs/InGaP quantum well lasers, and is comparable to the best result (200°C) reported for InGaAs/GaAs/AlGaAs lasers     

Temperature dependence of lasing wavelength in a GaInNAs laserdiode

The temperature dependence of lasing wavelength in 1.2-μm or 1.3-μm-range GaInNAs edge-emitting laser diodes (LD) was found to be small. It is almost independent of the characteristic temperature (T₀) and is equivalent to the temperature shift of the bandgap wavelength of GaInNAs (0.42 nm/°C). Since the dependence is smaller than that of 1.3-μm-range conventional InGaAsP LD's and also smaller than the required value (<0.48 nm/°C), it is concluded that the GaInNAs LD's are promising for use as 1.3-μm-range light sources because of their lasing-wavelength stability against temperature shift and a high T₀. The small dependence is due to the small effect of band filling on lasing wavelength from the deep quantum well in GaInNAs LD's